The linear guide device, as illustrated in FIG. 6, includes a guide rail 1, a slider 2, and plural rolling elements 3. The guide rail 1 and the slider 2 are arranged to oppose to each other, and respectively have rolling surfaces 11 and 21 for forming a rolling passage of the rolling elements 3. The slider 2 includes a return passage 22 of the rolling elements 3, and a direction changing passage for communicating the return passage 22 with the rolling passage. Then, a circulation path of the rolling elements is configured with the rolling passage, the return passage, and the direction changing passage. The rolling elements 3 circulating through this circulation path cause, and one of the guide rail 1 and the slider 2 relatively move in a linear manner to the other thereof.
The guide rail 1 of the linear guide device includes mounting holes 4 used for mounting the guide rail 1 onto a mounted part of a base or the like, by use of a bolt, not illustrated.
The mounting hole 4, as illustrated in FIG. 7, includes a counterbore part 41 for accommodating the head of the bolt, and a shaft accommodation part 42 for accommodating the shaft of the bolt. By inserting the bolt into the mounting hole 4 and threadedly engaging the bolt with the mounted part, the guide rail 1 is secured with the bolt to the mounted part, such as a base. Subsequently, in a conventional example, the upper part of the counterbore part 41 is closed with the cap, not illustrated, for the purpose of preventing entrance of a foreign material, such as burr.
The cap disclosed in Patent Literature 1 is known as an example of the cap. In a linear guide unit disclosed in Patent Literature 1, a plug for clogging a mounting hole on a top face of the raceway rail is provided. The plug is made of iron or stainless steel, includes a disc-shaped top plate part to be substantially flush with the top face of the raceway, and a cylindrical skirt part extending downward in a vertical direction from the top plate part. The outer circumferential part of the plug includes a lid part, which is an outer circumferential part of the top plate part, and which closes the mounting hole, a concaved circumferential groove part, which is an outer circumferential part of the skirt part, and which is made by reducing the thickness of the skirt part, and an engagement part, which is engaged and adhered to the mounting hole, and which includes an interference with the mounting hole.
In the linear guide unit disclosed in Patent literature 1 including the above-described plug, when the plug is inserted into the mounting hole, foreign materials such as burr generated from the engagement part can be prevented from moving to the top face of the raceway rail, by holding the materials in the concaved circumferential groove part.